Monolithic-integrated piezoresistive MEMS accelerometer pressure sensor with glass-silicon-glass sandwich structure

Abstract

Manuel Engesser et al. 2009) have been well developed and widely used in industrial and commercial applications. Recently, with the market expansion of electronic devices including automobiles, aerospace and portable electronics, great research effects have been motivated again to develop monolithic integrated silicon composite sensors that feature high reliability, low costs and mass fabrication capability (Wang et al. 2011(Wang et al. , 2012Xu et al. 2008;Roozeboom et al. 2013).This study aims at developing a novel monolithic composite MEMS sensor. The composite sensor integrated a piezoresistive pressure sensor and a piezoresistive accelerometer on one chip. It has a sandwich structure and is fabricated using bulk-micromachining process (Chen et al. 2009) and anodic wafer bonding technology (Liu et al. 2011;San et al. 2013). The accelerometer adopts double-cantilever-mass structure by which double cantilevers can lessen lateral sensitivity in insensitive direction and the mass can enlarge sensitivity in sensitive direction. The pressure sensor has rectangular diaphragm structure. The mass of accelerometer and the pressure-sensing diaphragm of pressure sensor are simultaneously wet anisotropic etched by using only one mask. Anodic bonding technology is used to seal the pressure-reference cavity for the pressure sensor and form the vacuum chamber for free motivation of accelerometer's cantilever-mass. Glass is bonded with the low pressure chemical vapor deposition (LPCVD) α-Si (amorphous silicon) layer in front side of wafer and with the silicon substrate in back side, respectively, to form sandwich structure. Around bonding areas in front side of wafer, trenches are designed and fabricated to ensure the electrical conduction between the LPCVD α-Si layer and the silicon substrate, which can protect the piezoresistors from p-n junction break-down during anodic bonding process in front side of wafer.Abstract A monolithic composite MEMS sensor with sandwich structure is designed, simulated, fabricated and characterized. It consists of a rectangular diaphragm piezoresistive pressure sensor and a double-cantilever-mass piezoresistive accelerometer. The professional MEMS software, Intellisuite 8.5, is used to simulate the performances of the composite sensor. The composite sensor is fabricated on a (100)-silicon wafer by using MEMS bulk-micromachining and anodic bonding technology. One-step wet anisotropic etching process on the backside of the wafer can form the main backside shape of the composite sensor including the mass of accelerometer and the pressure sensing diaphragm. The glass-silicon-glass sandwich structure is formed with α-Si (amorphous silicon)-glass anodic bonding on the top surface of the wafer and Siglass anodic bonding at the bottom. The fabricated composite sensor is measured, resulting in 33.0 μV/V kPa sensitivity for the 450 kPa-ranged pressure sensor, as well as, 11.2 μV/V g sensitivity for the 125 g-ranged accelerometer. The die size of the composite sensor chip is 2.5 mm × 2.5 mm × 1.4 mm. The...

Temperature Compensated Wide-Range Micro Pressure Sensor with Polyimide Anticorrosive Coating for Harsh Environment Applications

“…Therefore, the performance of a piezoresistive sensor depends largely on the pressure sensitive diaphragm. Firstly, the dimensions of the pressure sensor's diaphragm were designed based on previous published work [12]. Then, the thickness of the diaphragm was determined by theoretical calculation from Expression (1), where P burst is five times the maximum applied pressure, σ fracture is the maximum stress of the diaphragm, A is the area of the diaphragm, h is its thickness, and v is the Poisson's ratio.…”

“…In order to improve the performance of the micro piezoresistive pressure sensor, numerous studies have focused on optimization of structure, fabrication, and encapsulation. Dong et al [12] introduced a monolithic composite MEMS pressure sensor with an effective range of 450 kPa. Nag et al [13] modified the structure by integrating rod beams in a silicon diaphragm.…”

Fabrication and Characterization of Monolithic Integrated Three-Axis Acceleration/Pressure/Magnetic Field Sensors

“…A variety of multifunctional integrated sensors are available [ 1 ], including integrated temperature/humidity/air velocity sensors [ 2 ], integrated pressure/temperature sensors [ 3 , 4 ], integrated accelerometers and magnetometers [ 5 , 6 ], etc., which can be used in a wide range of applications in industrial fields [ 7 ], wearable devices [ 8 , 9 , 10 ], robot environments [ 11 , 12 ], and so on. Dong et al developed integrated acceleration and pressure multifunction sensors with a glass–silicon–glass sandwich structure based on piezoresistive effect, which can be applied to automobile, aerospace, environmental monitoring, and other application fields [ 13 ]. Wang et al proposed composite sensors with pressure and two-axis acceleration that have potential in the mass production of tire pressure monitoring systems (TPMS) with a sensitivity of 0.136 mV/kPa [ 14 ].…”

On-Chip Integration of Pressure Plus 2-Axis (X/Z) Acceleration Composite TPMS Sensors with a Single-Sided Bulk-Micromachining Technique

“…Compared with the hybrid packaging scheme for realizing simultaneous detection of pressure and acceleration, the latter scheme seems to be a good choice due to its advantages of smaller size, lower cost, higher reliability, and higher fabrication throughput. Thus far, various approaches, such as surface-micromachining [4,5,6], double-side bulk-micromachining [7,8], Cavity-SOI process [9], double-side CMOS post process [10], and MEMS-CMOS bonding process [11] have been developed and used to fabricate the on-chip integrating multifunctional sensor. Unfortunately, the fabricated sensors have more or less shortcomings [1], such as low sensitivity, large device-size, complex fabrication process, and high fabrication cost.…”